Thermal, mechanical and electrical properties of hard B4C, BCN, ZrBC and ZrBCN ceramics

We study the thermal, mechanical and electrical properties of B4C, BCN, ZrBC and ZrBCN ceramics prepared in the form of thin films by magnetron sputtering. We focus on the effect of Zrx(B4C)1−x sputter target composition, the N2+Ar discharge gas mixture composition, the deposition temperature and the annealing temperature after the deposition. The thermal properties of interest include thermal conductivity (observed in the range 1.3–7.3 W m−1 K−1), heat capacity (0.37–1.6×103 J kg−1 K−1 or 1.9–4.1×106 Jm−3 K−1), thermal effusivity (1.6–4.5×103 J m−2 s−1/2 K−1) and thermal diffusivity (0.38–2.6×10−6 m2 s−1). We discuss the relationships between materials composition, preparation conditions, structure, thermal properties, temperature dependence of the thermal properties and other (mechanical and electrical) properties. We find that the materials structure (amorphous×crystalline hexagonal ZrB2-like×nanocrystalline cubic ZrN-like), more than the composition, is the crucial factor determining the thermal conductivity and other properties. The results are particularly important for the design of future ceramic materials combining tailored thermal properties, mechanical properties, electrical conductivity and oxidation resistance.